215/50R18 vs 235/50R18

235/50R18 is 0.79 in (20.0 mm) taller than 215/50R18, a +2.98% diameter difference. With the speedometer set for 215/50R18, an indicated 60 mph is 61.8 mph on 235/50R18.

Is this a safe swap?

Diameter difference +2.98%: within the ±3% guideline

By overall diameter alone, 235/50R18 falls inside the ±3% range commonly used as a guideline when replacing 215/50R18. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

Side profile and tread width, drawn to the same scale.

215/50R18 vs 235/50R18 differences
Measurement	215/50R18	235/50R18	Difference	% diff
Overall diameter	26.46 in (672.2 mm)	27.25 in (692.2 mm)	+0.79 in (+20.0 mm)	+2.98%
Sidewall height	4.23 in (107.5 mm)	4.63 in (117.5 mm)	+0.39 in (+10.0 mm)	+9.30%
Section width	8.46 in (215.0 mm)	9.25 in (235.0 mm)	+0.79 in (+20.0 mm)	+9.30%
Circumference	83.14 in (2,111.8 mm)	85.61 in (2,174.6 mm)	+2.47 in (+62.8 mm)	+2.98%
Revolutions per mile	762	740	−22	−2.89%

True speed with the speedometer calibrated for 215/50R18
Indicated	Actual on 215/50R18	Actual on 235/50R18	Difference
30 mph	30.0 mph	30.9 mph	+0.9 mph
60 mph	60.0 mph	61.8 mph	+1.8 mph
75 mph	75.0 mph	77.2 mph	+2.2 mph

Ride-height change: 235/50R18 raises the vehicle by 0.39 in (10.0 mm) at the axle (half the +20.0 mm diameter difference).

235/50R18 is 0.79 in taller than 215/50R18 and 20 mm wider, a 2.98% difference in overall diameter.

With the speedometer calibrated for 215/50R18, an indicated 60 mph is actually 61.8 mph on 235/50R18, and revolutions per mile change from 762 to 740.

Both sizes mount on 18-inch wheels.

Size pages

Other comparisons with 215/50R18

Other comparisons with 235/50R18

Source: Calculated from standard tire geometry formulas. Verified 2026-09-27. How these numbers are calculated.